We plan to test the hypothesis that diurnal variations in the renin- angiotensin-system account for diurnal variations in the fibrinolytic system. Also, we plan to test the angiotensin converting enzyme (ACE) insertion/deletion and plasminogen activator inhibitor (PAI-1) 4G/5G polymorphisms affect PAI-1 and t-PA levels in African Americans and Caucasians.